U.S. patent number 4,368,245 [Application Number 06/205,564] was granted by the patent office on 1983-01-11 for method for making matt diffusion patterns.
This patent grant is currently assigned to Dr. Johannes Heidenhain GmbH. Invention is credited to Erich Bayer.
United States Patent |
4,368,245 |
Bayer |
January 11, 1983 |
**Please see images for:
( Certificate of Correction ) ** |
Method for making matt diffusion patterns
Abstract
A process for photolithographically producing matt diffusion
patterns is disclosed. The matt diffusion patterns can be formed
along with opaque and transparent patterns on the same pattern
carrier plate. According to this process, a photoexposure mask
corresponding to the desired matt pattern is made by
photolithography, which mask is then used in subsequent
photolithographic processes to form the matt diffusion pattern on
pattern carrier plates. The process of making the exposure mask
involves forming a mask of a desired diffusion pattern, applying a
photoresist layer to the mask, exposing the photoresist layer
through a diffusion plate, developing the photoresist layer,
applying an opaque layer to the mask, and removing the photoresist
layer. In subsequent photolithographic processes the exposure mask
is printed on transparent pattern carrier plates, and the exposed
areas of the pattern carrier plates are deeply etched to form the
matt diffusion patterns.
Inventors: |
Bayer; Erich (Trostberg,
DE) |
Assignee: |
Dr. Johannes Heidenhain GmbH
(Traunreut, DE)
|
Family
ID: |
6086111 |
Appl.
No.: |
06/205,564 |
Filed: |
November 10, 1980 |
Foreign Application Priority Data
|
|
|
|
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Nov 16, 1979 [DE] |
|
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2946235 |
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Current U.S.
Class: |
430/5; 430/314;
430/321; 430/323; 430/324; 430/326 |
Current CPC
Class: |
G02B
5/0221 (20130101); G03F 1/50 (20130101); G02B
5/0278 (20130101); G02B 5/0268 (20130101) |
Current International
Class: |
G02B
5/02 (20060101); G03F 1/14 (20060101); G03C
005/06 () |
Field of
Search: |
;430/5,321,313,312,316,314,327,329,323-326 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Louie, Jr.; Won H.
Attorney, Agent or Firm: Hume, Clement, Brinks, Willian
& Olds, Ltd.
Claims
I claim:
1. A process for the photolithographic production of a matt
diffusion pattern, the process comprising the following steps:
(a) providing a mask substrate having an opaque pattern formed
thereon;
(b) applying a mask photoresist layer to a face of the mask
substrate over the opaque pattern;
(c) exposing the mask photoresist layer through a matt diffusion
plate;
(d) developing the mask photoresist layer to remove portions
thereof;
(e) applying an opaque layer to the mask substrate face over the
remaining portions of the mark photoresist layer;
(f) removing the remaining portions of the mask photoresist layer
together with the overlying portions of the opaque layer to form an
exposure mask;
(g) applying an opaque layer to a face of a transparent carrier
plate;
(h) applying a carrier plate photoresist layer to the carrier plate
opaque layer;
(i) exposing the carrier plate photoresist layer through the
exposure mask;
(j) developing the carrier plate photoresist layer to remove
portions thereof;
(k) etching the carrier plate opaque layer to remove exposed
portions thereof;
(l) removing the remaining portions of the carrier plate
photoresist layer; and then
(m) deeply etching the exposed portions of the carrier plate face
to underetch and remove at least a portion of the remaining carrier
plate opaque layer and thereby to form an optically diffusing
patterned region.
2. The process of claim 1 wherein the diffusion plate is a plate of
glass having at least one face mechanically ground.
3. The process of claim 1 wherein the diffusion plate is a plate of
glass having at least one face chemically etched.
4. The process of claim 1 wherein at least one opaque layer is a
metal.
5. The process of claim 1 wherein at least one opaque layer is a
metal oxide.
6. The process of claim 1 further comprising the step of removing
at least part of the carrier plate opaque layer to form a
transparent pattern.
7. The process of claim 1 wherein the step of forming an exposure
mask of a diffusion pattern is performed photolithographically.
8. The process of claim 1 wherein step (m) comprises sufficient
under-etching to remove substantially all of the remaining carrier
plate opaque layer over the optically diffusing patterned
region.
9. A process for producing an exposure mask for the
photolithographic production of a patterned optical diffuser having
an optically diffusing region and an optically non-diffusing
region, said process comprising the following steps:
(a) providing an exposure mask substrate having an opaque pattern
formed thereon;
(b) applying a photoresist layer to a face of the mask substrate
aligned with the opaque pattern;
(c) exposing the photoresist layer through a diffusion matt plate
to form a pattern of exposed and unexposed regions on the
photoresist layer;
(d) developing the photoresist layer to remove portions thereof and
thereby to uncover underlying portions of the mask;
(e) applying an opaque layer over the remaining portions of the
photoresist layer and the uncovered underlying portions of the face
of the mask substrate; and then
(f) removing the remaining portions of the photoresist layer and
the portions of the opaque layer overlying the remaining portions
of the photoresist layer, thereby producing a pattern of remaining
portions of the opaque layer suitable for photolithographic
production of an optical diffusing region.
10. The process of claim 9 wherein the diffusion plate comprises a
ground glass plate.
11. The process of claim 9 wherein the opaque pattern formed on the
exposure mask corresponds to the optically non-diffusing regions in
the patterned optical diffuser produced thereby.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the United States counter-part of West German
Application Ser. No. P 29 46 235.9, dated Nov. 16, 1979, whose
priority is hereby claimed for this application.
BACKGROUND OF THE INVENTION
This invention relates to an improved method of making matt
diffusion patterns, in particular to methods of making matt
diffusion patterns along with opaque and transparent patterns. Such
diffusion patterns are utilized, for example, in photographic
camera view-finders, and on theodolite grid plates.
Hitherto, matt diffusion patterns have been made by applying the
desired pattern in the form of an opaque layer to a ground glass
pattern carrier plate. This process has not produced completely
satisfactory results, however, because holes have tended to form in
the opaque areas and thus to produce imperfect patterns. Also, this
means of producing patterns has the limitation that only matt and
opaque patterns can be produced thereby on a single carrier
plate.
SUMMARY OF THE INVENTION
The present invention is directed to a method of making matt
diffusion patterns which avoids these and other problems of the
prior art. In particular, the present invention is directed to a
photolithographical method of making matt diffusion patterns along
with either or both of opaque and transparent patterns on a
transparent pattern carrier plate.
According to this invention, a photoexposure mask corresponding to
the desired matt pattern is made by photolithography, which mask is
then used in subsequent photolithographic processes to form the
matt diffusion pattern on pattern carrier plates.
To generate the photoexposure mask, a photoresist layer is applied
to a mask of the desired matt diffusion pattern, exposed through a
matt diffusion plate, and developed. An opaque layer is then
applied over the mask, and the photoresist layer which remained
after developing, along with those portions of the opaque layer
lying thereon, is removed.
The photoexposure mask thus formed is used to photolitographically
create the desired matt diffusion pattern on the pattern carrier
plates. In a preferred embodiment of the invention, a transparent
pattern carrier plate has applied thereto an opaque layer. The
opaque layer is covered with a photoresist layer which is then
photographically exposed through the photoexposure mask described
above, and the photoresist layer is developed. The layer-bearing
face of the pattern carrier plate is then treated with etching
substances to etch away the opaque layer and the surface of the
pattern carrier plate in those areas which were exposed by
developing of the photoresist layer. The surface of the pattern
carrier plate is etched deeply so that the remaining opaque layer
is underetched slightly. This underetching removes small points of
the opaque layer from the matt diffusion pattern areas.
Finally, portions of the remaining opaque layer are removed to form
the transparent pattern.
One important advantage of this method of producing matted patterns
is that matt diffusion patterns can be produced along with both
transparent and opaque patterns on a single pattern carrier
plate.
Another advantage of this method of producing patterns is that matt
diffusion patterns can be produced along with transparent and
opaque patterns by means of using a single exposure mask.
Yet another advantage of this method is that improved patterns can
be made because holes no longer tend to form in the opaque portions
of the pattern.
The invention itself, together with further objects and attendant
advantages, will be best understood by reference to the following
detailed description taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1a through 1e show stages in the production of the exposure
mask.
FIG. 1a shows the photolithographic formation of the opaque
portions of the mask pattern;
FIG. 1b shows the exposure mask with the opaque portions of the
mask pattern formed;
FIG. 1c shows the exposure step of the photolithographic formation
of the diffusion portion of the mask pattern;
FIG. 1d shows the mask after application of the diffusion pattern
forming opaque layer;
FIG. 1e shows the final exposure mask.
FIGS. 2a through 2d show stages in the production of the matt
diffusion pattern on a pattern carrier plate;
FIG. 2a shows the carrier plate as it initially appears before
processing;
FIG. 2b shows the carrier plate after photolithographic processing
to imprint thereon the image of the exposure mask of FIG. 1e;
FIG. 2c shows the carrier plate after etching of the carrier plate
surface;
FIG. 2d shows the final pattern carrier plate with the matt
diffusion pattern.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawings, FIG. 1 shows stages in the formation
of the matt diffusion exposure mask 1.
As FIG. 1a shows, the exposure mask 1 is formed from a polished
transparent substrate or layer carrier 2 which carries on one face
an opaque layer 3. The opaque layer 3 is preferably a layer of
chromium. The opaque layer 3 is covered with a layer of
photoresistant photolacquer 4.
The photolacquer layer 4 is photographically exposed through an
auxiliary mask 5. The auxiliary mask 5 is opaque but for areas
which correspond to the desired final matt diffusion pattern, which
are either cut out of the auxiliary mask 5 or left transparent.
After exposure, the photolacquer layer 4 is developed to remove
those portions of the photolacquer layer that were exposed. Etching
substances are then applied to etch away those portions of the
opaque layer 3 which have no photolacquer layer 4 covering them.
After etching, the remains of the photolacquer layer 4 are removed.
Thus, exposure of the photolacquer layer 4 through the auxiliary
mask 5, followed by photolithographic processing, removes from the
opaque layer 5 the areas of the matt diffusion pattern of the final
diffusion plate, as shown in FIG. 1b.
The partially formed mask 1 of FIG. 1b is next covered with a new
layer of photolacquer 6 and is photographically exposed through a
matt diffusion plate 7, as shown in FIG. 1c. The matt diffusion
plate 7 is preferably a plate of glass with ground unpolished
surfaces.
The photolacquer layer 6 is developed to remove the exposed
portions of the photolacquer layer 6, and a new opaque layer 8 is
applied over the developed surface to produce the structure of FIG.
1d. The opaque layer 8 is preferably a metal or a metal oxide, most
preferably again a layer of chromium.
The remaining areas of photolacquer layer 6 are then removed, thus
removing also those areas of the opaque layer 8 which lie upon the
photolacquer layer 6, leaving behind as remains of the opaque layer
8 the opaque particles 9 as shown in FIG. 1e. The exposure mask 1
is now completed. Thus, exposure of the photolacquer layer 6
through the matt diffusion plate 7, followed by photolithographic
processing which, instead of the usual etching step, includes the
depositing of a new opaque layer 8, forms the exposure mask of FIG.
1e.
Chromium particles 9 adhere directly to the layer carrier 2 in
those areas of the pattern which are desired to be diffusing. Areas
desired to be transparent or opaque on the final pattern carrier
plate are opaque on the exposure mask 1.
FIG. 2 shows stages in the process of producing the matt diffusion
pattern on a pattern carrier plate, which process utilizes the
exposure mask of FIG. 1e.
FIG. 2a shows the unprocessed pattern carrier plate 14 which
comprises of a transparent carrier plate 10, an opaque layer 11
deposited on one face of the carrier plate 10, and a layer of
photoresistant photolacquer 12 covering the opaque layer 11. The
carrier plate 10 is preferably glass and the opaque layer 11 is
preferably chromium.
The photolacquer layer 12 is photographically exposed through the
exposure mask 1 to imprint therein the image of the exposure mask
1. The photolacquer layer 12 is then developed to remove the
exposed areas of the layer 12, and an etching substance is applied
to etch away those portions of the opaque layer 11 which are not
covered by photolacquer layer 12. This photolithographic process
forms in the opaque layer 11 the image of the exposure mask 1,
including opaque particles 13 which are an image of the opaque
particles 9 of the exposure mask 1, as shown in FIG. 2c.
Next, the remains of the photolacquer layer 12 are removed and an
etching substance is applied to etch away those portions of the
surface of carrier plate 10 which are not covered by opaque layer
11. The etching of the carrier plate 10 is made deep, so that the
opaque particles 13 are underetched, as shown in FIG. 2c, and thus
removed.
Removal of the opaque particles 13 by etching leaves the etched
surface areas of the carrier plate 10 jagged, as shown in FIG. 2d.
These jagged areas form the matt diffusion pattern on the pattern
carrier plate 14.
Finally, transparent areas of the final pattern are formed by
removing those parts of the opaque layer 11 which correspond to
those transparent areas. The formation of the transparent areas is
preferably again accomplished photolithographically.
The exposure mask 1 can be reused in subsequent photolithographic
processes to form additional diffusion plates 14.
This completes the production of the final pattern carrier plate in
which matt diffusion patterns have been formed along with opaque
and transparent patterns. Of course, it should be understood that
various changes and modifications to the preferred embodiment
described above will be apparent to those skilled in the art, which
changes and modifications can be made without departing from the
spirit or scope of the present invention.
* * * * *